Field of the Invention
The present disclosure relates to a camera module configured to be driven to one direction or to a bi-direction, and an auto focusing method of a camera module.
Description of Related Art
Recently, a mobile phone embedded with a super small digital camera and a tablet PC has been developed. A conventional super small digital camera used on a mobile phone has suffered from a disadvantage of disablement to adjust a gap between a lens and an image sensor changing an outside light to a digital image or a digital video (moving image). However, recently, a lens driving device, such as a VCM (Voice Coil Motor) capable of adjusting a gap between an image sensor and a lens, has been developed to obtain a digital image or a digital video that is more improved and advanced than that of a conventional super small digital camera.
Generally, a VCM (Voice Coil Motor) applied to a camera module is mounted therein with a rotor mounted with a lens, where the rotor vertically moves upwards from a base to adjust a gap between an image sensor arranged at a rear surface of the base and a lens of the camera. Recently, a bi-directional VCM has been developed capable of accomplishing an auto focusing by floating a rotor of the VCM from a base and moving the rotor downwards or upwards.
A conventional VCM is configured such that an elastic member depresses a rotor for contact with a base when no driving signal is applied. A rotor of a conventional bi-directionally driven VCM has an approximately 30 μm˜50 μm displacement depending on self-weight of the rotor and posture of the VCM.
However, the rotor according to the conventional bi-directionally driven VCM is disadvantageous in that, although the rotor has a displacement depending on the posture of the VCM, and even if no driving signal is applied, the rotor includes a non-driving section, the auto focus operation is performed by auto focusing algorithm not reflected with the displacement, thereby taking lots of time for auto focusing and consuming lot of currents.